In modern work vehicles, hydraulic circuits are used to power the hydraulic cylinders that manipulate work implements. Such systems may use pumps of the variable displacement type which control the flow rate of hydraulic fluid via manipulation of their displacement volumes. A displacement control valve is used to determine the direction of fluid flow to accomplish the desired work, i.e., for example, to positively extend or retract a double acting hydraulic cylinder. The displacement control valve is also used to allow free flow of fluid so as to minimize pressure generated, i.e., to enable floating; an operating mode in which an implement rests on and follows the contours of the earth as the work vehicle is propelled along the ground.
When a hydraulic cylinder is used to manipulate a tool or load against a resisting force such as gravity, the hydraulic pump for the associated hydraulic system, in a vast majority of cases, generates substantially less energy in moving to a retracted position than in moving to an extended position. This is generally due to the fact that the cylinder retracts under an action of gravity, but may extend only when the hydraulic cylinder overcomes the action of gravity. Moreover, the hydraulic cylinder uses less fluid and tends to generate less force during a retraction than during an extension as the internal volume and the area of application for generating a force load on the piston are smaller on the retracting side than on the extending side of the piston. Thus a hydraulic cylinder retraction may be generally characterized as a low energy phase of the hydraulic cylinder and an extension may be generally characterized as a high energy phase of the hydraulic cylinder.